Corneal heat and stretch method and apparatus

Abstract

A method and apparatus to alter the shape of the cornea of an eye provides for heating a portion of the cornea to a temperature not exceeding the collagen shrinkage temperature, and applying a pressure differential to a portion of the cornea. The combined effect of elevated temperature and stretching forces leads to permanent residual strains in preferred directions, and thus to a permanent new shape of the cornea. The method is applicable to the correction or reduction of myopia, hyperopia, and astigmatism.

What is claimed is: 
     
       1. A method of altering the shape of a subject eye, comprising the steps of: (a) heating a predetermined heating zone of the eye to a therapeutic temperature below a collagen shrinkage temperature,   (b) applying a therapeutic pressure differential within a predetermined treatment zone of the eye, thereby stretching collagen fibrils of the eye in predetermined directions.   
     
     
       2. The method of claim 1, wherein the heating (a) and applying (b) are maintained in a manner so as to permanently elongate collagen fibrils. 
     
     
       3. The method of claim 1, wherein the eye is a human eye, the collagen fibrils are in corneal tissue of the eye and the fibrils are heated to a temperature at or above that required to induce creep of the fibrils resulting in a permanent change in shape of the corneal tissue. 
     
     
       4. The method of claim 1, further comprising the steps of: (c) ceasing the applying (b) for a period of time while continuing the heating (a), and (d) repeating the applying (b) for a period of time while continuing the heating (a).   
     
     
       5. The method of claim 4, wherein the ceasing (c) and repeating (d) are carried out a plurality of times. 
     
     
       6. The method of claim 1, wherein the heating is heating by the application of a heated fluid. 
     
     
       7. The method of claim 6, wherein the fluid is an aqueous saline solution. 
     
     
       8. The method of claim 1, wherein the heating is heating by the directing of electromagnetic radiation. 
     
     
       9. The method of claim 8, wherein the electromagnetic radiation is infrared radiation primarily having a wavelength longer than about 1400 nm. 
     
     
       10. The method of claim 1, wherein the therapeutic temperature is in the range of about 37° C. to about 60° C. 
     
     
       11. The method of claim 1, wherein the therapeutic temperature is in the range of about 45° C. to about 55° C. 
     
     
       12. The method of claim 11, wherein the heating (a) is carried out for a period in the range of about 1 to about 5 minutes, and further wherein the pressure differential comprises a reduction of pressure in a predetermined suction zone on a surface of the eye and contact pressure in a predetermined contact zone on a surface of the eye, wherein the pressure in the suction zone is reduced in an amount in the range of about 100 mmHg to about 500 mmHg. 
     
     
       13. A method of changing cornea shape, comprising the steps of: (a) applying heat to a surface of an eye wherein heat is applied at a temperature and for a time sufficient to induce creep of the eye but insufficient to induce shrinkage of collagen fibrils of the eye;   (b) deforming the shape of the cornea by the application of a pressure differential whereby the deformed shape is maintained after the pressure is removed and the eye returns to body temperature.